Polyamide-based water-soluble biodegradable copolymers and the use thereof

ABSTRACT

Water-soluble, biologically degradable copolymers based on polyamide are described which contain at least one grafted side chain composed of aldehydes and sulfur-containing acids and salts thereof and optionally at least one compound from the series ketones, aromatic alcohols, urea (derivatives) and amino-s-triazines. Natural polyamides such as caseins, gelatins, collagens, bone glues, blood albumins and soya proteins as well as degradation products thereof and synthetic polyamides such as polyaspartic acids and copolymers of aspartic and glutamic acid are used as preferred polyamide components. These copolymers are obtained primarily by graft polymerization at temperatures between −10 and 250° C., preferably in the presence of a solvent such as water or by thermal drying and they are used in particular as flow agents or water retention agents for inorganic binders and pigments especially in combination with hydraulic binders they only have a very slight setting-retardant effect.

The present invention concerns water-soluble, biodegradable copolymersbased on polyamide and the use thereof.

Polycondensation products per se and in particular their use in thefield of construction chemicals are sufficiently well known in the priorart.

Thus polycondensates are used as so-called high performance flow agents.These include sulfonated aminoplast-formers, sulfonated naphthalene- andphenol-formaldehyde resins and sulfonated acetone-formaldehyde resins.

The patents DE 1 671 017 and DE 195 38 821 describe sulfonatedpolycondensation products of amino-s-triazines and formaldehyde;condensation products of triazines and glyoxylic acid are known fromU.S. Pat. No. 5,891,983. Polycondensation products of naphthalenesulfonic acids with formaldehyde are described in the patent documentsU.S. Pat. No. 2,141,569, DE 2 007 603 and EP 214 412. High-performanceflow agents which are obtained by reacting ketones with aldehydes havebeen previously described in U.S. Pat. No. 4,585,853.

Aqueous suspensions of inorganic powders such as clays, silicates orinorganic binders are often admixed in practice with additives forcertain applications. The flow agent group is used in this case toimprove the working properties of the suspensions to which they havebeen added. These additives are usually (poly)-electrolytes whichinfluence the rheological behaviour of the suspensions under shearingconditions:

The individual particles of the suspended material for example havesimultaneous positive and negative surface charges as a result of whichattractive coulombic forces act between the particles which leads to theformation of agglomerates and considerably increases the viscosity ofthe suspension. Due to their structure, the described additives adsorbto the surfaces of the suspended material. In doing so the polymericadditives neutralize either the positive or the negative component ofthe surface charge such that the individual solid particles in thesuspension electro-statically repel one another. This prevents theformation of agglomerates and existing agglomerates are broken up. Hencethe viscosity of the suspension is considerably reduced. In applicationsfor construction chemicals the described effect is used especially toproduce cement suspensions.

Many other suspended substances such as calcium sulfate binders, calciumcarbonate or various pigments have only positive or only negativesurface charges. In this case the electrolytic repulsion is increased bythe adsorption of poly-electrolytes to the particle surfaces.

In order to produce suspensions of hydraulic binders that can be easilyprocessed it is usually necessary to use considerably more water thanwould be required to chemically set the clinker. The excess waterevaporates after the setting and leads to a considerably less compact,hydrated phase which in turn results in a considerably reduced strengthof the hardened phase. By using flow agents it is possible to reduce theamount of water required while the working properties remain unchanged.This results in considerably improved compressive strengths of thehardened phases.

It is known that many of the polycondensates described in the prior artare usually not biologically degradable. Hence these compounds canaccumulate in the environment and contribute to soil or watercontamination.

This is particularly relevant when cement slurries for example come intocontact with drinking water or agricultural areas under cultivation. Inthis connection particular mention should be made to the use of flowagents in the exploration and production of crude oil or natural gas onthe high seas i.e. in so-called off-shore areas. Flow agents are usedhere for cementitious systems to construct drilling platforms and tocement bore holes. The flow agents that are used can in the former casebe washed out by sea water and in the latter case pass from the cementslurries into water-bearing formation layers. That is why preferenceshould be given to biodegradable products for applications in a marineenvironment according to the “Convention for the Protection of theMarine Environment of the North-East Atlantic” (OSPAR Convention).

Some biodegradable flow agents for cement slurries have already beendescribed in the prior art such as in U.S. Pat. No. 6,019,835 whichdiscloses modified ligno-sulfonates as biodegradable flow agents. Thealready published U.S. application 2002/0005287 describes polyasparticacid as a biodegradable high-performance flow agent.

Although these flow agents are biologically degradable, they usuallyhave the major disadvantage that they have a retarding effect on thesetting characteristics of cement slurries.

Hence the object of the present invention was to provide water-solubleand biologically degradable copolymers based on polyamide which can beused as high-performance flow agents and in doing so hardly retard thehydraulic setting of the clinker.

This object was achieved with appropriate copolymers which contain atleast one grafted side chain composed of aldehydes and sulfur-containingacids or salts thereof.

It was surprisingly found that the copolymers according to the inventioncan not only be used as flow agents in the high-performance field inaccordance with their intended function and generally have a lesspronounced retarding action, but that they also exhibit theiradvantageous properties under extreme conditions such as hightemperatures, high pressures and high salt concentrations which was notto be expected.

Moreover, it was completely unexpectedly found that the copolymersaccording to the invention are also suitable as water retention agents.Water retention agents are used to prevent water from escaping fromslurries of inorganic or organic binders or pigments. The water loss isusually due to capillary forces that emanate from porous substrates.Water retention agents can either bind water as a result of theirchemical structure or promote the formation of a thick filter cake onthe substrate.

Water retention binding agents are for example used for this purpose inplasters, tile cements, jointing mortars, knife fillers andself-levelling compounds as well as deep-well cement slurries. Inaddition they are also used among others in aqueous clay suspensionswhich can for example serve as drilling fluids. A number of compoundshaving such properties are known from the prior art. Thus EP-A 1090 889describes mixtures of clay and guar as water retention agents. DE-OS 19543 304 and U.S. Pat. No. 5,372,642 disclose cellulose derivatives aswater retention agents, EP-A 116 671, EP-A 483 638 and EP-A 653 547disclose synthetic polymers that contain acrylamido-substituted sulfonicacids as comonomers. However, all the described polymers are either notbiologically degradable or they are unstable at high temperatures. Incontrast the copolymers according to the invention are bio-degradableand they degrade at high temperatures to a considerably lesser extent.

Copolymers are regarded as preferred within the scope of the presentinvention which contain the polyamide component in proportions of 5 to80% by weight and preferably of 10 to 60% by weight, the aldehydecomponent in proportions of 5 to 90% by weight and preferably of 10 to70% by weight and the sulfur-containing acidic component in proportionsof 5 to 60% by weight and preferably of 15 to 40% by weight.

It has proven to be particularly advantageous when the new copolymershave natural polyamides especially in the form of caseins, gelatins,collagens, bone glues, blood albumins and soya proteins, syntheticpolyamides and here in particular polyaspartic acids or copolymers ofaspartic and glutamic acid as the polyamide component. The inventionalso encompasses polyamide components which have been derived from theabove-mentioned polyamides by oxidation, hydrolysis or depolymerizatione.g. by enzymatic degradation as well as any mixtures of the saidmembers.

The side chains grafted onto the copolymers are regarded as an essentialfeature of the invention whereby grafted aldehydes based onparaformaldehyde, paraldehyde and/or unbranched non-aromatic aldehydespreferably with 1 to 5 C atoms and in particular formaldehyde,acetaldehyde and glyoxal are preferred. Inorganic sulfur salts such asthose of sulfurous or disulfuric acid hence for example sulfites,hydrogen sulfites and disulfites of alkali (earth) metals, of aluminium,iron and ammonium are the preferred basis for the graftedsulfur-containing acids or salts thereof. Naphthalene- andbenzenesulfonic acids are preferred as organic sulfonic acids.

If inorganic sulfur-containing acids or salts thereof are used tosynthesize the polymers, preferably at least one additional compound isused in the case of the water-soluble and biologically degradablepolyamide-based copolymers according to the invention to build the sidechain(s).

In this case ketones and in particular those based on non-aromaticketones and especially 2-propanone, 2-butanone or pyruvic acid come intoconsideration as additional grafted compounds. However, grafted aromaticalcohols based on phenols, cresols, catechols or resorcins andaminoplast formers in particular dicyandiamide, amino-s-triazines andurea (derivatives) have also proven to be suitable for copolymersaccording to the invention. Particularly suitable amino-s-triazines arethose based on melamine (derivatives) and particularly preferably thosebased on melamine.

These additional compounds should be present in the copolymer sidechains preferably in proportions of 5 to 85% by weight and especially inproportions of 10 to 70% by weight.

Within the scope of the present invention especially copolymers thathave been produced by a special process have also proven to beparticularly advantageous:

In this process a graft polymerization is carried out preferably attemperatures between −10 and 250° C. and in particular between 0 and130° C. in each case preferably in the presence of a solvent and inparticular in the presence of a polar solvent such as water ordimethylsulfoxide.

However, the invention also takes into consideration the formation ofgraft polymers by thermal treatment such as by co-drying the polyamideand the polymer to be grafted.

Copolymers for which water or other polar solvents can be used to buildtheir side chains from the individual building blocks (grafting from)are especially suitable. Polymers having higher molar masses can bethereby obtained if either the process is carried out without water orwater is separated by distillation during the reaction.

In addition to the modification of the polyamide in solution it is alsopossible to carry out a bulk grafting. Polymers having a relatively highmolar mass are also obtained with this variant. If the aldehydes thatare to be grafted onto the polyamide are soluble in solvents that areimmiscible with water, the graft polymers can be synthesized byinterfacial condensation: for this purpose soya protein isolate is forexample dissolved in the aqueous phase and the low molecular weightcompounds that are to be grafted are dissolved in an organic phase.Vigorous intermixing of the two phases (e.g. by a Turax stirrer) allowsthe polycondensation to take place at the interface between the aqueousand organic phase.

However, the grafted copolymers according to the invention can also besynthesized by covalently linking the condensational addition productsto the polyamide backbone (grafting onto) which can also be carried outby reaction in solution or in bulk. In this case water ordimethylsulfoxide are again preferred as solvents.

In addition to the described methods for covalently linking the polymersin solution or in bulk, the copolymers can also be generated accordingto the invention during thermal co-drying of a solution which containsboth polymers. In this case water comes primarily into consideration asthe solvent. The drying process is best carried out by spray-drying ordrum-drying.

All grafting reactions should be carried out in a temperature rangebetween −110° C. and 250° C. If it is carried out in solution, atemperature range between 0° C. and 130° C. is preferred. The procedurecan be carried out at normal pressure but also at an increased pressure.

In addition to the grafted copolymers themselves and the preferablyproduced variants thereof, the present invention also claims their useas flow agents for inorganic binders and pigments and in particular asflow agents for hydraulic binders. In this connection it should again bementioned that the copolymers according to the invention are primarilycharacterized by the fact that they only have a low tendency to delaysetting. Thus for example it has turned out that the copolymers used asflow agents result in a considerably reduced setting time for cementslurries compared to polyaspartic acid.

In addition the present invention also claims the use of the polymersaccording to the invention as water retention agents. Also in this casethe short setting time that can be achieved with polymers according tothe invention is an advantage.

Overall there are no limitations whatsoever on the molecular weight ofthe copolymers according to the invention, but certain ranges haveproven to be indeed advantageous for special intended purposes. If theclaimed copolymers are used as flow agents, they should according to thepresent invention have a molar mass {overscore (M)}_(n) of <50,000g/mol. If the copolymers according to the invention are used as waterretention agents, a molar mass {overscore (M)}_(n) of >50,000 g/mol hasproven to be advantageous and molar masses {overscore (M)}_(n)of >80,000 g/mol are particularly suitable.

With regard to the use of the proposed copolymers, the present inventionalso envisages their combination with modified and/or unmodifiedpolysaccharides where modified celluloses and in this case in particularhydroxyalkylcelluloses with C₁₋₄ alkyl residues are regarded asparticularly preferred. In this variant of the invention synergisticwater retention effects are achieved independent of the molar mass ofthe copolymers according to the invention which is remarkable in view ofthe copolymers having an {overscore (M)}_(n) of <50,000 g/mol whichuniquely exhibit a flow agent effect in this size range within the scopeof the invention.

Water-soluble, biologically degradable copolymers are described based onpolyamide which contain at least one grafted side chain composed ofaldehydes and sulfur-containing acids and salts thereof and optionallyat least one compound from the series ketones, aromatic alcohols, urea(derivatives) and amino-s-triazines. In this case natural polyamidessuch as caseins, gelatins, collagens, bone glues, blood albumins andsoya proteins as well as degradation products thereof and syntheticpolyamides such as polyaspartic acids and copolymers of aspartic andglutamic acid are used as preferred polyamide components. Thesecopolymers are obtained primarily by graft polymerization attemperatures between −10 and 250° C., preferably in the presence of asolvent such as water or by thermal drying, and they are used inparticular as flow agents or water retention agents for inorganicbinders and pigments especially in conjunction with hydraulic binderswhere they retard the setting only to a slight extent.

The following examples illustrate the advantages of the water-solubleand biologically degradable copolymers based on polyamide according tothe invention.

EXAMPLES EXAMPLES OF PREPARATION Example 1

20 g casein was dissolved in 210 g water and 17.5 g sodium sulfite and16.5 g acetone were added. The reaction solution was then heated to 60°C. and 80 g of a 30% aqueous formaldehyde solution was added dropwise.Subsequently it was stirred for a further 2 h at 70° C. and the pH ofthe reaction solution was adjusted with formic acid to pH 7.0. Thereaction solution was finally concentrated in a vacuum to half itsvolume in order to remove the methanol formed by the competing Canizarroreaction.

Example 2

240 g gelatin was dissolved in 600 g water and 100 g sodium sulfite and100 g acetone were added. The reaction solution was heated to 60° C. and360 g of a 30% aqueous formaldehyde solution was added. Subsequently thereaction solution was stirred for about 2 h at 80° C. and the pH wasadjusted to ca. 7.0 with formic acid. The reaction solution wasconcentrated in a vacuum to half its volume in order to remove themethanol formed by the competing Canizarro reaction.

Example 3

100 g sodium sulfite and 100 g acetone were dissolved in 250 g water.The reaction solution was heated to 60° C. Afterwards 467 g of a 30%aqueous formaldehyde solution was added. Subsequently the reactionsolution was stirred for 40 min at 70° C. and 7.26 g sodium pyrosulfitewas added to the reaction solution and it was then stirred for a further30 min. The pH of the reaction solution was adjusted with formic acid toa pH of ca. 7.0. The reaction solution was concentrated in a vacuum tohalf its volume in order to remove the methanol formed by the competingCanizarro reaction. The reaction solution was diluted with 6 l distilledwater and 340 g casein was stirred in. The resulting polymer solutionwas dried which initiated the grafting.

Example 4

100 g soya protein isolate was added to 600 g water. The pH was adjustedto ca. 13 with sodium hydroxide. Subsequently 104 g sodium sulfite and98 g acetone were added and the reaction mixture was heated to 80° C.356 g of a 30% formaldehyde solution was added dropwise and the reactionsolution was stirred further. The pH of the reaction solution wasadjusted with formic acid to pH 7.0. The reaction solution wassubsequently concentrated in a vacuum to half its volume in order toremove the methanol formed by the competing Canizarro reaction.

Example 5

15.9 g polyaspartic acid was dissolved in 100 g water. The solution wascooled to about 2° C. Subsequently 34.8 g sodium sulfite and 36.0 gpyrocatechol were added. Then 40.9 g acetaldehyde was added dropwisesuch that the temperature of the mixture did not exceed 12° C. Afteraddition of the acetaldehyde was completed, the reaction temperature wasincreased to 75° C. and the reaction solution was stirred at thistemperature for a further 2 hours. The solution was cooled to 20° C.,adjusted to pH 7.0 with formic acid and concentrated in a vacuum toabout half its volume.

Example 6

39.77 g gelatin was added to 100 ml dimethylsulfoxide. Subsequently 17.4g sodium sulfite and 16.4 g urea were stirred in. The mixture was heatedto 60° C. and then 6.9 g of a 40% aqueous glyoxal solution was added.The reaction solution was heated to 75° C. and kept at this reactiontemperature for two hours. The dimethyl-sulfoxide was removed underreduced pressure.

Example 7

150 g of a 30% aqueous formaldehyde solution was added first and heatedto 30° C. After adding 63 g melamine and 50 g sodium pyrosulfite, 95 gof a 15% sodium hydroxide solution was added. Subsequently the reactiontemperature was increased to 75° C., 280 g water was added, the pH wasadjusted to ca. 3.0 with sulfuric acid, 79 g of a 40% aqueous solutionof polyaspartic acid was added and it was stirred for a further twohours at 75° C. The reaction solution was concentrated at 80° C. underreduced pressure to ca. one third. Afterwards the pH was increased toca. 7.0 with sodium hydroxide solution.

EXAMPLES OF APPLICATION Example 8

The plasticizing effect of the copolymers according to the invention oncement slurries containing commercial building cement was determinedwith the aid of the slump factor. For this 1.5 g polymer was dissolvedin 140 g tap water and subsequently 300 g cement (CEM 1 42.5 R) wasadded. The slurries were allowed to stand for 60 sec and then stirredvigorously for 120 sec. The slurries were poured up to the brim of aVicat ring (H=40 mm, d_(small)=65 mm, d_(large)=75 mm) that stood on aglass plate. The Vicat ring was lifted 2 cm and held for about 5 secover the slurries that flowed out. The diameter of the slurries that hadflowed out was measured on two perpendicular axes. The measurement wasrepeated once. The arithmetic mean of all four measurements gives theslump factor. The following slump factors were obtained: TABLE 1 PolymerSlump factor (according to example) [cm] — 15 1 24 2 25 3 19 6 22

Example 9

The retarding effect of the copolymers according to the invention on thesetting properties of salt-containing cement slurries was examined usingthe following formulation:

792 g cement (CEM I 32.5) was mixed with 1.0% by weight copolymer. 77 gsodium chloride was dissolved in 308 ml water. The cement/copolymermixture was stirred into the salt water and transferred into anatmospheric consistometer (Chandler Engineering, Tulsa, Cat. No.12-95-1) at 90° C. The setting time was determined at 90° C. The sodiumsalt (PAS) of polyaspartic acid was used as a reference (table 2). TABLE2 Polymer Hardening time (according to example) [h:min] — 1:05PAS >6:00  2 3:07 3 4:30 7 5:10

Example 10

The start and end of solidification of the copolymers according to theinvention in salt-free cement slurries was determined according to Vicat(DIN EN 196-3). For this 500 g cement (CEM I 42.5 R) was mixed with 210g tap water and 2.5 g copolymer. The mixture was homogenized and thecement slurries were subsequently measured. TABLE 3 Polymer Settingstart Setting end (according to example) after [h:min] after [h:min] —6:30  7:50 1 7:00 11:30 2 7:50 11:20

Example 11

The plasticizing effect of the copolymers according to the invention incalcium sulfate slurries was determined with the aid of the slumpfactor. 2 g copolymer was dissolved in 180 g tap water and subsequently500 g α-semihydrate (CaSO₄.0.5 H₂O) was added. The slurries were allowedto stand for 60 sec and then vigorously stirred for 45 sec. The slurrieswere poured up to the brim of a Vicat ring (H=40 mm, d_(small)=65 mm,d_(large)=75 mm) that stood on a glass plate. The Vicat ring was lifted2 cm and held for about 5 sec over the slurries that flowed out. Thediameter of the slurries that had flowed out was measured on twoperpendicular axes. The measurement was repeated once. The arithmeticmean of all four measurements gives the slump factor. A slump factor of23 cm was obtained for the copolymer of example 1. Without addition ofthe copolymer the slump factor was 13 cm.

Example 12

The dispersing action of the copolymers according to the invention insalt-containing slurries was investigated as follows:

700 g cement (Joppa Lafarge Class H) was mixed with 0.5% bwoc of thecopolymer and subsequently stirred into 364.4 g salt water (27% byweight NaCl). The cement slurries were conditioned for 20 min at 38° C.Subsequently the plasticizing effect of the copolymers according to theinvention was determined with the aid of a FANN 35 SA rotationviscometer (r_(rotor)=1.8415 cm, r_(stator)=1.7245 cm, h_(stator)=3.800cm, d_(ring gap)=0.1170 cm). The values obtained were compared withthose of a slurry without a plasticizing additive (−) and with a slurrycontaining polyaspartic acid (PAS) (table 4). TABLE 4 Shear stress Shearstress Polymer at Viscosity at at Viscosity at (according to {grave over(y)} = 511 s⁻¹ {grave over (y)} = 511 s⁻¹ {grave over (y)} = 10.2 s⁻¹{grave over (y)} = 10.2 s⁻¹ example) Pa mPas Pa mPas — 38.3 75 8.7 850PAS 28.1 55 3.1 300 1 22.0 43 1.5 150 2 22.5 44 1.0 100 3 25.6 50 2.6250 5 33.2 65 3.1 300 6 25.0 49 3.1 300

Example 13

The polymers according to the invention are suitable as water retentionagents for plaster pastes. The water retention capacity of the plasterpastes treated with the polymers according to the invention wasdetermined according to DIN 18 555. 350 g α semihydrate was mixed with210 g tap water, 0.25 g Retardan® (retarder for plasters from theTricosal Company, Illertissen) and 2.5 g of the copolymer according toexample 4 and homogenized. A water retention capacity of 70.9% (blankvalue 41.5%) was achieved.

Example 14

The polymers according to the invention are suitable as water retentionagents for cement slurries. The water retention capacity of the cementslurries treated with the polymers according to the invention wasdetermined according to DIN 18 555. 350 g CEM I 42.5 R cement was mixedwith 210 g tap water and 2.5 g of the copolymer according to example 4and homogenized. The water retention capacity of the cement slurries was84.6% (blank value 63.8%).

Example 15

The biodegradability of the copolymers according to the invention wasdetermined according to OECD 306. The biodegradabilities after 28 dayswere determined from the ratio of the biological to theoretical oxygenrequirement and compared with the biodegradability of polyaspartic acid(PAS) (table 5). TABLE 5 Polymer Biological degradability according toexample) after 28 days in % PAS 35% 2 38% 3 42%

Example 16

The synergistic effect of the copolymers according to the inventiontogether with modified polysaccharides with regard to the waterretention capacity was examined using the following cement slurries.

700 g cement (Joppa class H) was mixed with 0.25% by weighthydroxyethylcellulose and 1.0% by weight of the copolymer 2, in eachcase based on the cement content and subsequently stirred into 266 gwater. The cement slurries were conditioned for 20 min at 88° C. Thewater retention capacity was examined according to API spec. 10 at 70bar and 88° C. The values obtained were compared with those of theslurries without copolymer or without hydroxyethylcellulose. Whereas awater loss of 350 ml occurred without copolymer and a water loss of 250ml occurred without hydroxyethylcellulose, the combined use of bothpolymers resulted in a water loss of only 60 ml.

1-18. (canceled)
 19. A copolymer comprising at least one grafted sidechain composed of aldehydes and sulfur-containing acids or saltsthereof, wherein the copolymer is water-soluble, biologically degradble,aminoplast former-free, and is based on polyamide.
 20. A copolymers asclaimed in claim 19, wherein they contain the polyamide component inproportions of 5 to 80% by weight, the aldehyde component in proportionsof 5 to 90% by weight and the sulfur-containing acidic component inproportions of 5 to 60% by weight.
 21. A copolymers as claimed in claim19, wherein the polyamide component natural polyamides, particularlypreferably caseins, gelatins, collagens, bone glues, blood albumins,soya proteins and degradation products thereof formed by oxidation,hydrolysis or depolymerization, and synthetic polyamides or mixturesthereof.
 22. A copolymer as claimed in claim 21, wherein the polyamidecomponent is a polyaspartic acid or copolymers of aspartic and glutamicacid and degradation products thereof formed by oxidation, hydrolysis ordepolymerization as well as mixtures thereof.
 23. A copolymers asclaimed in claim 19, comprising a grafted aldehyde based onparaformaldehyde, paraldehyde or unbranched non-aromatic aldehydesformaldehyde, acetaldehyde and glyoxal.
 24. A copolymer as claimed inclaim 19, comprising a grafted aldehyde having from 1 to 5 carbon atoms.25. A copolymer as claimed in claim 19, comprising formaldehyde,acetaldehyde or glycoxal.
 26. A copolymers as claimed in claim 19,wherein that they contain grafted sulfur-containing acids (salts) basedon inorganic sulfur salts.
 27. A copolymer according to claim 26,wherein the grafted sulfur containing acid is a sulfite, hydrogensulfite a disulfites of an alkali metal or aluminium, iron or ammonium.28. A copolymer as claimed in claim 19, wherein that the side chainfurther comprises at least one compound from the series ketones andaromatic alcohols.
 29. A copolymers as claimed in claim 28, comprisingadditional compound is/are present in proportions of 5 to 85% by weight.30. A copolymers as claimed in claim 28, comprising grafted ketonesbased on non-aromatic ketones 2-propanone, 2-butanone or pyruvic acid.31. A copolymers as claimed in claim 28, comprising grafted aromaticalcohols based on phenols, cresols, catechols or resorcins.
 32. Acopolymers as claimed in claim 19, produced by graft polymerization attemperatures between −10 and 250° C.
 33. The copolymer of claim 29,wherein the graft polymerization is conducted in the presence of asolvent.
 34. A composition comprising an inorganic binder and thecopolymer of claim
 19. 35. The copolymer of claim 28, wherein said graftpolymerization is by thermal treatment.
 36. The copolymer of claim 19,wherein the copolymer has a molar mass {overscore (M)}_(n) o of <50,000g/mol.
 37. The copolymer of claim 33, wherein said solvent is a polarsolvent.
 38. The copolymer of claim 37, wherein said polar solvent iswater is dimethyulsulfoxide.
 39. A copolymer as claimed in claim 19,wherein they contain the polyamide component in proportions of 10 to 60%by weight of the aldehyde component in proportions of 10 to 70% byweight by weight and the sulfur-containing acidic component inproportions of 15 to 40% by weight.